Focus control in continuous shooting in digital photographing apparatus

Abstract

A digital photographing apparatus includes a focus lens, a focus detection unit that detects focus in a contrast auto focusing (AF) method by moving the focus lens, and a controller that calculates a velocity of a subject from a first focus detection result and a second focus detection result in a continuous shooting operation. The controller restricts a U-turn driving for correcting backlash of the focus lens when the calculated velocity of the subject is equal to or greater than a predetermined value. An AF initiating location and a final correction operation are adaptively adjusted based on the velocity of the subject in each process of the continuous shooting, thereby improving an AF performance and the continuous photographing speed.

What is claimed is: 
     
       1. A digital photographing apparatus comprising:
 a focus lens; 
 a focus detection unit that detects focus in a contrast auto focusing (AF) method by moving the focus lens; and 
 a controller that calculates a velocity of a subject from a first focus detection result and a second focus detection result in a continuous shooting operation, and that restricts a U-turn driving for correcting backlash of the focus lens when the calculated velocity of the subject is equal to or greater than a predetermined value; 
 wherein the controller calculates a difference between the first focus detection result and the second focus detection result, and when the difference is equal to or greater than a predetermined value, the controller restricts the U-turn driving that is performed for correcting the backlash of the focus lens. 
 
     
     
       2. The digital photographing apparatus of  claim 1 , wherein the controller drives the focus lens to a location that is obtained by adding a backlash correction value to the detected focus, if the U-turn driving is restricted. 
     
     
       3. The digital photographing apparatus of  claim 2 , wherein the velocity of the subject is calculated based on at least two or more focus detection results. 
     
     
       4. The digital photographing apparatus of  claim 1 , wherein the velocity of the subject is calculated based on at least two or more focus detection results. 
     
     
       5. The digital photographing apparatus of  claim 1 , further comprising:
 an imaging device that is exposed to light incident through the focus lens and reads-out an image signal; and 
 a controller that sets an AF initiating location based on the first focus detection result and the second focus detection result in a continuous shooting operation, and that moves the focus lens to the AF initiating location during the read-out of the imaging device. 
 
     
     
       6. The digital photographing apparatus of  claim 5 , wherein the controller predicts a location of a subject by calculating a difference between the first focus detection result and the second focus detection result, and sets the AF initiating location based on the predicted location of the subject. 
     
     
       7. A method of controlling a continuous shooting operation of a digital photographing apparatus, the method comprising:
 detecting focus in a contrast auto-focusing (AF) method by moving a focus lens; 
 calculating a velocity of a subject based on a first focus detection result and a second focus detection result in a continuous shooting operation; and 
 restricting a U-turn driving that is performed to correct backlash of the focus lens, when the calculated velocity of the subject is equal to or greater than a predetermined value; 
 wherein a difference between the first focus detection result and the second focus detection result is calculated, and when the difference is equal to or greater than a predetermined value, the U-turn driving that is performed for correcting the backlash of the focus lens is restricted. 
 
     
     
       8. The method of  claim 7 , wherein in the restricting of the U-turn driving, the focus lens is moved to a location that is obtained by adding a backlash correction value to the detected focus. 
     
     
       9. The method of  claim 7 , further comprising:
 exposing an imaging device to light that is incident through the focus lens, and performing a read-out; and 
 setting an AF initiating location based on the velocity of the subject, and moving the focus lens to the AF initiating location during the read-out of the imaging device, before the restricting of the U-turn driving. 
 
     
     
       10. A non-transitory computer-readable recording medium having embodied thereon a program for executing a method of performing a continuous shooting method by using a contrast auto-focusing (AF) method, the method comprising:
 detecting focus in the contrast AF method by moving a focus lens; 
 calculating a velocity of a subject based on a first focus detection result and a second focus detection result of a continuous shooting operation; and 
 restricting a U-turn driving that is performed for correcting backlash of the focus lens when the velocity is equal to or greater than a predetermined value; 
 wherein a difference between the first focus detection result and the second focus detection result is calculated, and when the difference is equal to or greater than a predetermined value, the U-turn driving that is performed for correcting the backlash of the focus lens is restricted.